Using an output driver circuit such as an output buffer circuit having an output preset circuit in an integrated circuit for driving an output data is quite common nowadays. For example, please refer to FIG. 1, it shows a schematic circuit diagram of an output preset circuit for an output buffer circuit as disclosed by Ishibashi et al. in the U.S. Pat. No. 4,992,677. In FIG. 1, the output preset circuit includes two voltage references (VH and VL), two differential amplifiers (Op1 and OP2), two NMOS (M1 and M2) and a capacitor C (an output load), and a terminal of each of VH, VL, M2 and C is connected to a ground. VH, VL, OP1 and OP2 are used to detect the output level of a voltage of C, and M1 and M2 are employed to preset the voltage of C to VH or VL. M2 is turned on and M1 is turned off to pull low the voltage of C to VH when the voltage of C is higher than VH, and M1 is turned on and M2 is turned off to pull up the voltage of C to VL when a voltage of C is lower than VL.
The main drawbacks of the output preset circuit as shown in FIG. 1 are that the two differential amplifiers OP1 and OP2 are complex in their interior configurations and cause higher power consumptions, and also two extra voltage references VH and VL are generated. Although, this output preset circuit does have the advantages of having the high read out speed and the low switching noise.
Facing the challenges of the energy crisis and the global warming nowadays and coping with the trend of having higher density of electronic elements and lower power consumptions in an IC, the purpose of the present invention is to find an output preset circuit with the advantages of having high read out speed, low switching noise and lower power consumption.
Keeping the drawbacks of the prior arts in mind, the applicant proposes an output driver circuit with an output preset circuit and controlling method thereof having lower power consumption.